Manufacturing Of Fiber Reinforced Composites Research Articles

Создание новых композиционных материалов для 3D-печати на основе полиимидных связующих и непрерывного углеродного волокна

Three-dimensional printing of composites reinforced by continuous fiber and based on heat-resistant materials requires a prepreg compatible with these plastics. This kind of a prepreg, in its turn, would necessarily have to be similar to these plastics in terms of its chemistry and operational thermal range. This work was an investigation of factors relevant for the strength of adhesion between carbon fiber and polymeric binder. The authors managed to develop the compounds (coupling agents) facilitating fiber impregnation with polymer and improving fiberbinder adhesion. To obtain a thermoplastic binder various polyimide matrices have been synthesized. The properties of polymers thus created were studied as per the methods of thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC), as well as measurement of limiting wetting angle. Then these materials were subject to solution impregnation so as to obtain prepreg samples suitable for 3D printing. Impregnation quality of these samples was studied by means of scanning electronic microscopy. The most promising prepreg samples were used for 3D printing of try-out product specimens. Composites based on the plastics reinforced by continuous fibers (glass, carbon, polymeric, etc.) are widely used in special fields of today’s technology [1–4]. They have already become indispensable for rocketry or aircraft industries, and they are steadily gaining ground in other industries, too, like machine engineering, shipbuilding, civil engineering, etc. Polymeric composite have become so popular because they are quite strong [5, 6] and light [7] at the same time. Today, manufacturing of fiber-reinforced composites is quite tedious and only allows a limited scope of geometries for final products [8] because fiber impregnation with viscous solutions/melts of polymers is a difficult process. Besides, final product takes time to harden, so until it happens it needs a moulding cast or skeleton to maintain its shape. This tedious process of product manufacturing from the parts reinforced with continuous fiber might proceed much easier and with greater automation thanks to 3D printing as per fused deposition modeling (FDM) technique that uses a filament of preimpregnated fiber [9]. In particular, one of the techniques steadily improving today is 3D printing with continuous carbon fiber and prepregs based on epoxy binders. Final products manufactured as per this technology and reinforced by continuous carbon fiber feature stable size and complex shape. However, prepregs based on epoxy resins will work only with the materials that have good adhesion with them, otherwise final composites will be too weak. Current materials can only be used for the products with low operational temperatures whereas hi-tech applications require strong and heat-resistant materials. To meet this requirement, it is necessary to develop prepregs based on heat-resistant compounds, as well as filaments based on heat-resistant plastics compatible with these prepregs. Polyimides as a class of compounds have long been known to remain stable at high temperatures. Therefore, prepregs based on them, as well as polyimide matrices fit for FDM 3D printing technique will pave way to the products simultaneously featuring high thermal resistance and good strength. The purpose of this work was to develop prepregs based on carbon fiber and polyimides featuring good resistance to high temperatures and aggressive media, as well as to develop thermoplastic polyimide matrices fit for 3D printing.

Orientation control and nonlinear trajectory tracking of colloidal particles using microfluidics

Suspensions of anisotropic Brownian particles are commonly encountered in a wide array of applications such as drug delivery and manufacturing of fiber-reinforced composites. Technological applications and fundamental studies of small anisotropic particles critically require precise control of particle orientation over defined trajectories and paths. In this work, we demonstrate robust control over the two-dimensional (2D) center-of-mass position and orientation of anisotropic Brownian particles using only fluid flow. We implement a path-following model predictive control scheme to manipulate colloidal particles over defined trajectories in position space, where the speed of movement along the path is a degree of freedom in the controller design. We further explore how the external flow field affects the orientation dynamics of anisotropic particles in steady and transient extensional flow using a combination of experiments and analytical modeling. Overall, this technique offers new avenues for fundamental studies of anisotropic colloidal particles using only fluid flow, without the need for external electric or optical fields.

FRACTAL CHARACTERS OF PORE MICROSTRUCTURES OF TEXTILE FABRICS

It is found that the pore microstructures of textile fabrics, widely used in the manufacture of fiber-reinforced composites, exhibit the fractal characters. The fractal behaviors are described by the proposed analytical method and measured by the box-counting method for the three different types of textile fabrics: plain woven, four-harness, bidirectional-stitched fiberglass mats. The pore area fractal dimension is derived analytically and found to be the function of the porosity and architectural parameters of fabrics. The results indicate that the fractal characters are isotropic although the fabrics are rothotropic in structures. The theoretical predictions by the proposed analytical model are in good agreement with those from the box-counting method, and this verifies the proposed fractal dimension model. The present fractal analysis may have the potential and significance on fractal analysis of transport properties (such as the permeability, dispersion, thermal and mechanical properties) in porous media.

Manufacture of fiber‐reinforced composites by microwave assisted pultrusion

AbstractA brief review of the potential for microwave heating in the manufacture of fiberreinforced composites is presented, with particular emphasis on the Microwave Assisted Pultrusion (MAP). Manufacture of a 6 mm cylindrical glass reinforced profile, based on a number of latent‐cure epoxy resins by MAP is described. These materials combine room temperature stability (long pot life) with rapid crosslinking at elevated temperature. The measured line speeds exceeded 2 m/min, using approximately 800 W of applied microwave power in a single mode TM010 cavity operating at 2450 MHz. The measured pulling force was about 250 N, showing a stick‐slip behavior for a crosslinked profile. The ultimate tensile strength and the interlaminar shear strength of the profiles increased after post curing, suggesting that the extent of crosslinking in the MAP die may be diffusion limited.

The impact of pultrusion processing parameters on resin pressure rise inside a tapered cylindrical die for glass-fibre/epoxy composites

Pultrusion is a continuous process with application in the manufacture of fiber-reinforced composites. This work is focused on understanding the impact of various pultrusion process control parameters on the pressure-rise phenomenon inside a cylindrical die for glass-fibre/epoxy composites. The important process control parameters in pultrusion manufacturing are the pull speed, fiber volume fraction, viscosity, die heating zones temperature settings, and pre-form plate area ratio (compaction ratio). The pressure rise in the die inlet contributes to a major extent in enhancing fiber wet-out and suppressing void formation in the manufactured composite. A numerical model for evaluating the pressure-rise behavior inside the die inlet is developed on the basis of Darcy's law since the resin flow through the fibers is similar to the flow through porous media. A fixed control-volume-based finite-difference method known as the finite-volume method is employed to solve the governing equations of a three-dimensional axis-symmetric cylindrical die inlet geometry. Also, a variable viscosity model is used to compute the viscosity in the straight portion of the die.

Polymer selection and matrix aspects of processing and manufacture of fibre composites

A multitude of matrix resin types, fibres and processes are currently used in the manufacture of fibre-reinforced composites. With particular reference to glass, aramid and carbon fibre-reinforced epoxies, the factors which determine the selection of the best matrix resin for a given application are discussed. The effect of resin type on the processing and production of the composite is considered. Finally, the manufacturing and performance criteria of low viscosity and controlled high viscosity epoxy matrices are compared and contrasted.